Wot you need is a camera pointing into the throat of the carb that you can trigger from inside the car and note at what revs you are taking each pic, then you could see how high the needle has risen out of the jet.
Vizard's book tells you roughly what each bit does but only roughly. A rolling road session is the only way of being absolutely sure but then, as I discovered, a rolling road can be very artificial. I had one on mine and it did improve things but it still didn't leave the car perfect.
It wasn't cheap then and now Lord knows what they cost. Also you need to know the guy who does it. At least mine was a renowned Mini specialist.
But then, (as I found out later, too late) he tuned mine for racing rather than simply driving around the place.

As always, it is a learning experience.
So I like the idea of an AFR gauge but without being able to put it together with revs and needle position it is a bit of a poser. In the sense of "a difficult problem". (God I do speak old English sometimes). Maybe money better spent on a range of needles that you think might better "fit" what you are aiming for.